First, I would also ask your pediatrician, as they know exactly how your twins are doing, and would have excellent suggestions. :) Additionally, I know you say they've started cereal. Do you mean just the instant flakey stuff you put milk or water in? If so, I'd start with rice puffs or cheerios, etc. If they get one at a time, they usually wet it until it is soggy before they swallow it, and that is a more solid food. I would also just start making the things they already get in baby food, and mush them up to a little more grainy than the baby food. You can then control the consistency, and it can change over time. Mashed carrots (very cooked), and pototoes, etc. work well. Also, regular applesauce, not the baby food jars, etc. Do you have a blender? Use that for what you normally eat together. But, whatever you do, make the change slowly, and in addition to what they are already getting, so that you know the transition is smooth and workable. I hope this helps. Good luck, and congrats on having two healthy twin babies. :)
J.